Thousands of strokes could be prevented each year by switching at-risk patients to a new type of blood-thinning drug, the results of a major trial suggest.
Researchers compared the effects of standard warfarin and the new medication, dabigatran etexilate, in a group of 18,000 patients from 44 countries.
All had atrial fibrillation (AF), a common heart rhythm disorder that greatly increases the chances of blood clots and strokes.
The study found that the new drug reduced the risk of stroke in high-risk patients by 30pc more than warfarin.
It also demonstrated significantly better performance with low and medium-risk patients.
Annual stroke rate was reduced by up to 90pc in AF patients when the effects of dabigatran were compared with receiving no treatment at all.
A major problem with warfarin -- traditionally used as rat poison -- is that doses have to be constantly measured and monitored to prevent potentially harmful bleeding.
Warfarin's effect is also reduced by eating certain foods rich in vitamin K, including broccoli, cabbage and asparagus. The drug can also interact with other medicines.
For these reasons, warfarin is often not given to patients, or treatment is stopped.
Dabigatran avoids many of these problems and is said to be far easier to manage.
Sold under the brand name Pradaxa, the drug is expected to become generally available in August, and will be significantly more expensive than warfarin. Currently it can only be prescribed to prevent blood clots after hip and knee replacement surgery.
Dr Adrian Brady, consultant cardiologist at Glasgow Royal Infirmary, called the results "exciting and highly significant".
"I think we're talking about preventing thousands of strokes a year if this drug becomes widely available," he said.
"We estimated that 50pc of all people with AF in the UK who should be on an anti-coagulant are not given warfarin because of concerns about bleeding."
The drug was the first major advance in controlling blood clotting in 50 years, he said.
Two or three similar drugs were in the pipeline and still at the laboratory stage.